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|標題:||Preparation and Characterization of Thermo- / pH- responsive Hollow Nanospheres
溫度 / 酸鹼應答型中空奈米膠粒的製備及性質探討
|作者:||Shun, Lee Chia
|關鍵字:||Thermo- / pH- responsive;溫度 / 酸鹼應答;Hollow Nanospheres;中空奈米膠粒||出版社:||化學工程學系||摘要:||
本製程為設計一以自由基聚合反應所製備之接枝型高分子，此高分子在特定條件下（I = 0.1 M、pH 3.0，及溫度 = 60 ℃時），可在水溶液中自組排列形成微胞，並以微胞外層vinyl group交聯形成穩定的溫度 / 酸鹼應答型外層交聯式奈米膠粒。
組成包括以2-hydroxyethacrylate （HEMA）單體與poly N-acry- loxysuccinimide（polyNAS）主鏈進行轉酯化反應， 將vinyl group導入polyNAS主鏈，使此高分子能行交聯反應。並以poly N-isopro- pylacrylamide（PNIPAAm）和methoxylpolyethylene glycol （mPEG）為接枝側鏈，利用amide鍵結將此兩種接枝側鏈與polyNAS主鏈進行反應，接枝PNIPAAm可利用其LCST性質製備膠粒，且使膠粒具有溫度敏感性。接枝mPEG則能增加膠粒結構於液相時穩定性，以及避免膠粒與膠粒間的聚集現象產生，並將NAS上之五環水解為AAc，使膠粒具有酸鹼應答的效果。
經由FTIR及1H-NMR的定性以及定量分析結果，可以驗證側鏈高分子與前驅高分子的結構及組成。以TNBS測量法計算結果mPEG-NH2的轉化率達95 ％；PNIPAAm-NH2的分子量則為1,400、1,900，及2,700。而前驅高分子主鏈上PNIPAAm-NH2的接枝率達80 ％，mPEG-NH2的接枝率則為63 ％，轉酯化的比例是90 ％，且經由圖譜分析證實無誤。
另外由DSC熱流圖、UV / VIS穿透度變化圖，以及高分子水溶液粒徑變化圖，可知其LCST並不會隨著組成而改變，且60 ℃下亦不會影響APS交聯劑的作用，故找出較佳製備條件為60 ℃、I = 0.1、pH 3.0下進行膠粒合成。
Under the conditions （I＝0.1、pH 3.0，and LCST = 60℃ aque- ous solution）, the graft copolymer described below self-assembles to micelles. External vinyl groups are then used to cross link the micelles to form shell-cross-linked naonparticles which are pH and temperature responsive.
The vinyl group have been introduced into a polyNAS polymer main chain by transesterfication with 2-hydroxyethacrylate（HEMA）monomer. poly N-isopropylacrylamide（PNIPAAm）and methoxylpoly- ethylene glycol（mPEG）side chains have been introduced into poly- NAS main chain too.
Introducing PNIPAAm into the polymer has two propose. The LCST property（1）allow the micelles to form and（2）lets the micelles become temperature responsive. Hydrolysis of the succinimid side chain of NAS to AAc results in a pH responsive micelles. Grafting PEG-NH2 onto the polymer increases the colloidal stability by preventing interparticle interactions.
FTIR and NMR were used to determine the structure and composition of the side chain polymers and prepolymer. The conversion of mPEG-NH2 and the Mw of PNIPAAm were quantified by TNBS and were 90 ％ and 1,400、1,900、2,700 g/mol. Conversions rates were quantified with NMR and were 80 ％ for the PNIPAAm graft, 50 ％ for the PEG graft, 90 ％ for the ester transesterfication.
Also, by DSC、UV/VIS spectrophotometry and DLS experiments. We determined the LCST dose not change with different Mws of PNIPAAm. Since, the effectiveness of APS is not affect at 60 ℃,（the temperature at which there are no further changes in conformation of the micelle）, we determined （I＝0.1、pH 3.0，and LCST = 60℃ aqueous solution）to be the best reaction conditions.
The particle size and distribution were found by DLS. We also found that the particle size increased with increasing Mw of PNIPAAm side chain. Particle size decreased in acid conditions and increased in basic conditions . Regardless of the Mw of PNIPAAm side chain, we found that the LCST shifted to 35℃ for all particles and the responsive temperature range widered. Thus the nanoparticles have high temperature and pH sensitivity.
The shape was determined by FE-SEM、TEM, and AFM and was found to be a hollow sphere, In the dry state, particles were evenly dispersed and non-aggregated. Particle size was found to be 70 nm, which makes these particles potential nano scale drug carriers.
|Appears in Collections:||化學工程學系所|
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